This invention relates to a receiver for use in a time diversity electrical communication system.
In a time diversity electrical communication system, each signal bit carrying an information piece, such as a logic "1" or "0" value, is repeatedly transmitted a predetermined number of times from a transmitter to one or more receivers. The information piece is reproduced in the receiver with diversity reception carried out with respect to time. The time diversity communication is often resorted to, particularly when errors are liable to occur intermittently in the information pieces during transmission of the signal bits from the transmitter to the receiver through a transmission path.
As will later be described with reference to a few figures of the accompanying drawing, a conventional receiver of a time diversity communication system comprises a circuit for judging the information pieces carried by the respective received signal bits. On reproducing the information piece carried in common by the repeatedly transmitted and received signal bits, it is assumed that no appreciable errors are introduced into a majority of the information pieces carried by the received signal bits to keep the information piece nearly correct although considerable errors may appear in a minority to render the information piece incorrect. A majority logic circuit therefore decides the correct information piece by majority of the judged information pieces. The receiver, however, is not applicable to a system in which the signal bit is repeatedly transmitted an even number of times because decision by majority becomes infeasible when one and an alternative information pieces are judged to be equally probable. Although well operable for a system in which the signal bit is transmitted an odd number of times, the receiver is not sufficiently reliable because the assumption is not always applicable. For a system in which each signal bit is transmitted twice, an alternative conventional receiver comprises an Exclusive OR circuit for finding a coincidence between two information pieces obtained from a pair of repeatedly received signal bits to decide the correct information piece. The alternative receiver, however, is again unreliable because the Exclusive OR circuit gives correct results only when the two information pieces are nearly correct.